This invention relates to a magnetic brush support member, the process of making it and a magnetic brush apparatus incorporating the support member. The support member is formed of a composite which imparts improved abrasion resistance to the surface of the member which supports the magnetic brush.
Magnetic brush apparatuses are employed in electrostatographic machines for a variety of purposes including developing and cleaning. U.S. Pat. Nos. 3,040,704 and 3,246,629 describe apparatuses used for developing electrostatic images. In the apparatuses described, the magnetic brush support member comprises a cylindrical sleeve which is rotatably supported about a stationary magnetic. The sleeve and magnet comprise a magnetic brush roll. When the roll is brought into operative contact with developer particles which include ferromagnetic particles, the particles are attracted to the surface of the cylindrical sleeve and arrange themselves thereon in the form of a brush. The brush is employed to bring toner particles which adhere to the ferromagnetic particles into contact with an electrostatic image in order to develop the image by transfer of the toner particles to the image areas so as to render them visible. It is apparent from the teachings of these patents that ferromagnetic particles or other similar metal particles used as a carrrier in the developer exert an abrasive influence on the surface of the mag brush roll. Further, it is apparent, that it is desirable for the rolls to have a roughened surface so as to prevent the particles from slipping. Mechanically roughening the roll surface or cutting grooves, or knurls in the surface are inadequate since the number of bristle sites are restricted. Further the abrasive action of the carrier on the roll surface polishes down the surface roughness thereby reducing the effectiveness of the surface. The preferred materials for the sleeve are non-magnetic metals such as aluminum, brass and other relatively soft alloys and these are rapidly worn down by the abrasive action of the developer mix.
In accordance with the teachings of U.S. Pat. No. 3,246,629, a separate coating is provided on the surface of the non-magnetic sleeve which comprises a layer of particulate matter of powdered materials such as glass, ceramic, plastic and various metals including ferrous metals. The layer may be applied by adhering a layer of irregular particulate matter using a matrix of bonding adhesive or by flame spraying the particulate matter on the roll surface.